GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 STS 🢒 Steering 🢒 Steering Wheel and Column 🢒 DTC P2105

Circuit Description

The engine control module (ECM) controls the throttle valve by applying a varying voltage to the control circuits of the throttle actuator control (TAC) motor. The ECM monitors the duty cycle that is required to actuate the throttle valve. The ECM monitors the throttle position (TP) sensors 1 and 2 to determine the actual throttle valve position. If the ECM detects the incorrect voltage level at the ignition 1 voltage supply circuits, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2105 Throttle Actuator Control (TAC) System - Forced Engine Shut down

Conditions for Running the DTC
    • The ECM power down process in the last drive cycle completely finished.
    • DTC P2105 runs continuously once the above condition is met.

Conditions for Setting the DTC

The ECM detects the incorrect voltage level at the ignition 1 voltage supply circuits.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines if the condition exists. If DTC P2105 sets, the engine will stall and not restart until the ignition is cycled OFF and then ON. Additional DTCs set when P2105 sets. The ignition key will not be able to be removed from the ignition switch until another ignition cycle occurs.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the ignition, with the engine OFF.
  2. Clear the DTCs with a scan tool.
  3. Start the engine.
  4. Rapidly, move the accelerator pedal from the rest position to wide open throttle position. It may take a few attempts for the DTC to set.
  5. Observe the DTC information with a scan tool.

Does DTC P2105 fail this ignition?

Go to Step 4

Go to Step 3

3
  1. Observe the Freeze Frame/Failure records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure records data.

Did the DTC fail this ignition cycle?

Go to Step 4

Go to Intermittent Conditions

4

Important: The fuse must be removed to inspect for an open. Voltage will be available at both terminals at the fuse block, because of a normal voltage back feed condition.

Inspect the engine control module (ECM) or the HFV6 ECM fuse for being open.

Is the fuse open?

Go to Step 5

Go to Step 6

5

    Important: This DTC will only set if the fuse is open and the circuits are not grounded. The ignition 1 voltage circuits must be tested thoroughly for an intermittent short to ground.

  1. Test both ignition 1 voltage circuits between the fuse and the ECM for an intermittent short to ground. Refer to Circuit Testing and Wiring Repairs .
  2. Replace the fuse.

Did you find and correct the condition?

Go to Step 9

Go to Intermittent Conditions

6

Test for an open ignition 1 voltage circuit between the ECM or the HFV6 ECM fuse and the splice. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 7

7

Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 8

8

Replace the ECM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 9

--

9
  1. Turn OFF the ignition for 30 seconds.
  2. Start the engine.
  3. Reset the fuel trim system with a scan tool.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 10

10

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK